To remove a repeating data structure from the study, all repeating data instances must be deleted first. 

Attempting to delete a repeating data structure with existing instances will result in a warning message: “You cannot delete this repeating data yet. There are X repeating data instance(s) created for this repeating data. You must first delete all instances. Note: Deleting instances is only possible for studies that have never been set to live.” See example on the screenshot below:

Once there are no repeating data instances left in the study, the repeating data structure itself can be removed. 

If the study has never been set to 'live', just delete the active and archived repeating data instances. Afterwards, you will be able to delete the repeating data structure in the ‘Study structure’ tab.

If you have created a participant and there are also repeating data forms in it, In the global or participant 'Repeating data' tab you can see if there are still repeating data and you can delete them. 

Additionally, please consider the following:

• It might be necessary to remove the Repeated Measure fields in your study forms that use this repeating data.
• In addition, check if you have deleted all repeating data for all sites, as in some cases you might not be able to see the repeating data for the sites for which you do not have relevant rights.
• Lastly, please keep in mind that if the study has been set to live, according to GCP it is not possible to delete the repeating data structure anymore. In this situation you can either rename the unwanted repeating data so that users do not create  instances, or blind users from it.